Known solar concentrator systems usually comprise heavy reflector elements made of glass and/or metal which are expensive to manufacture because their shape must be finished very accurately. In the past, it has been proposed to make use of lighter foil mirrors instead of the heavy glass or metal mirrors. Thereby, a metallized foil is tentered over a frame made of fibre composite material and brought into a parabolic shape. Thus, the weight of such a mirror element is approximately one quarter of the weight of a comparable mirror element made of glass or metal. Such a solar concentrator system comprises an essentially inexpensive, lightweight concentrator incorporating a metallized plastic foil with fixed focus. On the other side, the frame must be precisely and expensively manufactured to the calculated shape whereby even minor deviations from the ideal or theoretically required shape result in a substantial degradation of the efficiency of the system.